On 18 July 2014, the starboard forward mezzanine deck on board the UK registered roll-on roll-off passenger ferry St Helen partially collapsed, causing injuries to a crewman and several passengers. UK MAIB has issued investigation report which reveals that the failed wire rope had suffered a significant amount of mechanical wear. The mechanical wear, which had primarily been attributed to internal and external abrasion caused by a lack of lubrication, had severely diminished the strength of the rope.
St Helen was berthed at the Fishbourne ferry terminal, Isle of Wight, and the mezzanine deck was being lowered in preparation for the disembarkation of the cars parked on it. The injured crewman, who was rendered unconscious from a head injury, and three passengers, who had suffered a variety of minor injuries while seated in their cars, were taken to hospital. None of the injured remained in hospital overnight.
The mezzanine deck collapsed when its inboard steel wire ramping rope suddenly parted. This caused the forward inboard corner of the suspended deck to drop from a height of about 2m and hit the main deck below. The force of the impact caused the failure of one of the mezzanine deck’s main structural beams.
The investigation found weaknesses in the way that Wightlink had managed the day-to-day maintenance of its vessels and, in particular, their mezzanine decks. This was despite the mezzanine decks being subject to regular inspections and mandatory 6-monthly thorough examinations by a Royal & Sun Alliance Engineering Inspection & Consultancy surveyor.
Conclusions
- St Helen’s starboard forward mezzanine deck collapsed because one of its steel wire lifting ropes parted.
- The rope parted under normal working conditions.
- The parted rope had suffered excessive internal and external mechanical wear. This had caused a reduction in the cross-section of the rope’s individual wire strands to a point where it could no longer support the weight of the loaded deck.
- St Helen’s mezzanine decks had not been maintained in accordance with the equipment manufacturer’s instructions. This allowed the material condition of the collapsed deck to deteriorate to a dangerously unsafe condition.
- The material condition of the collapsed deck’s wire rope sheaves increased the stresses acting on the lifting wires and contributed to the rope failure.
- Wightlink’s mezzanine deck greasing routines had fallen into abeyance and their steel wire lifting ropes had not been routinely dressed and lubricated over many years.
- Wightlink’s maintenance management system had weaknesses in key areas. In particular: maintenance roles and responsibilities were confused, record keeping was inconsistent and time was not allocated for the conduct of some essential maintenance.
Further details may be found by reading the report
Source: UK MAIB